1. Field of the Invention
The present invention relates to a fuel cell and, in particular, to a fuel cell with its cells disposed in a planar arrangement.
2. Description of the Related Art
A fuel cell is a device that generates electricity from hydrogen and oxygen so as to obtain highly efficient power generation. A principal feature of a fuel cell is its capacity for direct power generation which does not undergo a stage of thermal energy or kinetic energy as in conventional power generation. This presents such advantages as high power generation efficiency despite the small scale setup, reduced emission of nitrogen compounds and the like, and environmental friendliness on account of minimal noise or vibration. A fuel cell is capable of efficiently utilizing chemical energy in its fuel and, as such, environmentally friendly. Fuel cells are therefore envisaged as an energy supply system for the twenty-first century and have gained attention as a promising power generation system that can be used in a variety of applications including space applications, automobiles, mobile devices, and large and small scale power generation. Serious technical efforts are being made to develop practical fuel cells.
In particular, polymer electrolyte fuel cells feature lower operating temperature and higher output density than the other types of fuel cells. In recent years, therefore, the polymer electrolyte fuel cells have been emerging as a promising power source for mobile devices such as cell phones, notebook-size personal computers, PDAs, MP3 players, digital cameras, and electronic dictionaries and books. Well known as the polymer electrolyte fuel cells for mobile devices are planar fuel cells, which have a plurality of single cells arranged in a plane. And as a fuel to be used for this type of fuel cells, hydrogen stored in a hydrogen storage alloy or a hydrogen cylinder, as well as methanol, is a subject of continuing investigations.
With a planar fuel cell with its cells arranged in a plane, the total area of catalysts is proportional to the electric power. On the other hand, the voltage depends on the number of cells connected in series. Accordingly, in order to downsize the fuel cell and obtain necessary power and voltage, the spacing between catalyst layers needs to be as small as possible and the a catalyst area needs to be as large as possible. However, as the spacing between the catalyst layers gets smaller and shorter, a problem of short-circuiting arises.
In the forming of catalyst layers disposed at fine intervals, laser processing is useful but there is a problem where the laser processing cuts off the bonding of side chains in a molecular structure of electrolyte membrane. Also, as the heat caused by the laser processing transfers across the electrolyte membrane, there is another problem where the electrolyte membrane deteriorates. When such a structural alteration and deterioration occur in the electrolyte membrane and also hydrogen is used as fuel, a problem arises where the hydrogen leaks and the performance of fuel cell deteriorates.